PROCEDE D'EXPOSITION A LA LUMIERE D'UNE COMPOSITION DE RESINE PHOTOSENSIBLE

PROCESS FOR EXPOSING A PHOTOSENSITIVE RESIN COMPOSITION TO LIGHT

Abrégé anglais

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ABSTRACT
The present invention provides an improved process
by which dissolved oxygen is effectively removed from a
photosensitive resin layer of a photosensitive resin
plate. The process comprises preliminary exposing to light
the photosensitive resin plate to quench oxygen dissolved in
said photosensitive resin layer before conducting a main
exposure, wherein the photosensitive resin layer is prepared
from a photosensitive resin composition which comprises,
(a) a polymer binder,
(b) a radically polymerizable monomer,
(c) a sensitizing dye, and
(d) a photopolymerization initiator which is
excited by a light of a different wave length from
a light exciting the sensitizing dye,
the preliminary exposure is conducted with a light only
exciting the sensitizing dye and the main exposure is
conducted with a light exciting the photopolymerization
initiator.

Revendications

-20-
WHAT IS CLAIMED IS
1. A process for exposing a photosensitive resin
plate comprising a substrate and a photosensitive resin
layer on said substrate, comprising preliminary exposing to
light said resin plate to quench oxygen dissolved in said
photosensitive resin layer and then conducting a main
exposure, wherein said photosensitive resin layer is
prepared from a photosensitive resin composition which
comprises;
(a) a polymer binder,
(b) a radically polymerizable monomer,
(c) a sensitizing dye, and
(d) a photopolymerization initiator which is
excited by a light of a different wave length from
a light exciting said sensitizing dye,
said preliminary exposure is conducted with a light only
exciting said sensitizing dye and said main exposure is
conducted with a light exciting said photopolymerization
initiator.
2. The process according to Claim 1 wherein said
polymer binder (a) has a polymerization degree of 10 to
300,000.
3. The process according to Claim 2 wherein said
polymer binder (a) has a molecular weight of 100 to
1,000,000.
4. The process according to Claim 1 wherein said
polymer binder (a) contain a radically polymerizable group.

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5. The process according to Claim 1 wherein said
polymer binder (a) is selected from the group consisting of
polyvinyl alcohol, partially saponified polyvinyl acetate,
cellulose polymer, polyacrylamide, polyvinyl pyrrolidone and
a homopolymer or copolymer of butadiene, chloroprene, 1,3-
pentadiene, styrene, vinyl acetate, ethylene, (meth)acrylic
ester, acrylonitrile, acrylic acid and/or methacrylic acid.
6. The process according to Claim 1 wherein said
radically polymerizable monomer (b) is selected from the
group consisting of (meth)acrylates, (meth)acrylamide and a
mixture thereof.
7. The process according to Claim 1 wherein said
sensitizing dye (c) is selected from the group of xanthenes,
thiazines, chlorophills, quinones, indigos, porphyrins,
ruthenium complexes and a mixture thereof.
8. The process according to Claim 1 wherein said
photopolymerization initiator (d) is selected from the group
consisting of benzoin alkyl ether, benzophenones,
acetophenones, camphorquinone and a mixture thereof.
9. The process according to Claim 1 wherein said
photosensitive resin composition further comprises a solvent
and additives.
10. The process according to Claim 1 wherein said
photosensitive resin composition comprises 0.0001 to 5 parts
by weight of said sensitizing dye (c) and 0.01 to 15 parts
by weight of said initiator (d), based on 100 parts by
weight of the total of said binder (a) and the monomer (b).

-22-
11. The process according to Claim 1 wherein said
weight ratio of the monomer (b) / the binder (a) is within
the range of 0.1 /99.9 to 99,9/0.1.
12. The process accordlng to Claim 1 wherein said
sensitizing dye (c) and said initiator (d) satisfy the
following relation, if the maximum absorption wave length of
said the sensitizing dye (c) is expressed as .lambda.max(c) and
that of said initiator (d) is expressed as .lambda.max(d):
.lambda.max(c) 450 to 800 nm
.lambda.max(d) = 300 to 400 nm
<IMG>
13. A photosensitive resin composition for the
process of Claim 1 comprises;
(a) a polymer binder,
(b) a radically polymerizable monomer,
(c) a sensitizing dye, and
(d) a photopolymerization initiator which is
excited by a light of a different wave length frorn
a light exciting the sensitizing dye.
14. The process according to Claim 13 wherein said
polymer binder (a) has a polymerization degree of 10 to
300,000.
15. The process according to Claim 24 wherein said
-polymer binder (a) has.a molecular weight of 100 to
1,000,000 .
16. The composition according to Claim 13 wherein
said polymer binder (a) contain a radically polymerizable

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group.
17. The composition according to Claim 13 wherein
said polymer binder (a) is selected from the group
consisting of polyvinyl alcohol, partially saponified
polyvinyl acetate, cellulose polymer, polyacrylamide,
polyvinyl pyrrolidone and a homopolymer or copolymer of
butadiene, chloroprene, 1,3-pentadiene, styrene, vinyl
acetate, ethylene, (meth)acrylic ester, acrylonitrile,
acrylic acid and/or methacrylic acid.
18. The composition according to Claim 13 wherein
said radically polymerizable monomer (b) is selected from
the group consisting of (meth)acrylates, (meth)acrylamide
and a mixture thereof.
19. The composition according to Claim 13 wherein
said sensitizing dye (c) is selected from the group of
xanthenes, thiazines, chlorophills, quinones, indigos,
porphyrins, ruthenium complexes and a mixture thereof.
20. The composition according to Claim 13 wherein
said photopolymerization initiator (d) is selected from the
group consisting of benzoin alkyl ether, benzophenones,
acetophenones, camphorquinone and a mixture thereof.
21. The composition according to Claim 13 wherein
said photosensitive resin composition further comprises a
solvent and additives.
22. The composition according to Claim 13,
comprising 0.0001 to 5 parts by weight of said sensitizing
dye (c) and 0.01 to 15 parts by weight of said initiator

- 24 -
(d), based on 100 parts by weight of the total of said
binder (a) and the monomer (b).
23. The process according to Claim 13 wherein sai.d
weight ratio of the monomer (b) / the binder (a) is within
the range of 0.1 /99.9 to 99.9/0.1.

Description

-- 1 --
- 21~3~22
PROCESS FOR EXPOSING A PHOTOSENSITIVE
RESIN COMPOSITION TO LIGHT
FIELU OF THE INVENTION
The present invention relates to a process for
exposing a photosensitive resin composition to light when
printing.
BACKGROUND OF THE INVE:NTION
Photosensitive resin compositions generally cure
through radical polymerization, upon exposing to light. The
curing reaction is inhibited by oxygen which is dissolved in
the resin compositions, because the oxygen functions as a
radical scavenger. It is therefore necessary that the
dissolved oxygen is removed from the resin composition
before exposure.
The removal of the dissolved oxygen can be
conducted by placing the photosensitive resin plates in an
atmosphere of carbon dioxide gas or nitrogen gas overnight
before exposure in order to replace the dissolved oxygen
with carbon dioxide or nitrogen gas. This method takes a
long time and needs a large space for a machine.
Practically conducted methods are those wherein the resin
plates are preliminary exposed (or bumped) with weak light
to quench the dissolved oxygen and then subjected to a main
exposure. The preliminary exposure (or bump) requires
specific conditions limited for only quenching the dissolved
oxygen, for example exposing time, irradiated light density
and the like. In addition, if the photosensitive resin

2~3~2~
layer has a thickness of more than 0.1 mm, the weak light
does not sufficiently reach to the side of the substrate, at
which the removal of the dissolved oxygen is insufficient.
In the following main exposure, this side will not cure
sufficiently due to the remaining oxygen. Accordingly,
after developing, isolated dots have barrel-like shapes and
thin toward the substrate, thus resulting in the decline of
durability. If the dissolved oxygen is tried to be quenched
sufficiently at this side in the preliminary exposing
process, the surface which faces to light would start to
unnecessarily cure. Also, it the main exposure is conducted
for a longer period of time in order to sufficiently cure
the side of substrate, the etching depth of white portions
and dot portlons is shallow and the printing portions are
thicker than negative images. It also takes a long period
of time to produce printing plates and ununiformity of
poIymerization reaction reduces the durability of the
printing plates.
SUMMARY OF THE INVENTION
The present invention provides an improved process
by which dissolved oxygen is effectively removed from a
photosensitive resin layer of a photosensitive resin
plate. The process comprises preliminary exposing the
photosensitive resin plate to light to quench oxygen which
~5 is dissolved in said photosensitive resin layer before
conducting a maln exposure, wherein the photosensitive resin
layer is prepared from a photosensitive resin composition

~ ~ 3 ~ ~ 3322
which comprisesi
(a) a polymer binder,
(b) a radically polymerizable monomer,
(c) a sensitizing dye, and
(d) a photopolymerization initiator
the preliminary exposure is conducted with a light only
exciting the sensitizing dye, and the main exposure is
conducted with a light exciting the photopolymerization
initiator.
The present invention also provides a
photosensitive resin composition for the above mentioned
process, comprising;
(a) a polymer binder,
(b) a radically polymerizable monomer,
(c) a sensitizing dye, and
(d) a photopolymerization initiator which is
excited by a light of a different wave length from
a light exciting the sensitizing dye.
DETAILED DESCRIPTION OF T~E INVENTION
The polymer binder (a) employed in the present
invention is added to control a physical properties and
chemical properties of the obtained resin composition and a
hardness of a cured material. The binder (a) preferably has
a polymerization degree of 10 to 300,000, preferably 50 to
3,000 and, if necessary, contain a radically polymerizable
group therein. It also has a molecular weight of 100 to
1,000,000, preferably 5,000 to 500,000, determined by GPC

- 4 - ~J~
method. If the binder contains particles, they have a
particles siæe of 0.01 to 5 micron, preferably 0.02 to 1
micron. The presence of the radically polymerizable group
enhances durability, ink resistance and solvent resistance
of obtained printing plates. Examples of the binder (a) are
a water soluble polymer binder not having an ionic group,
such as polyvinyl alcohol, polyamide resin, cellulose resin,
a modified resin thereof, etc.; a water-soluble or water-
dispersible polymer bidner having an ionic group or a
nonionic hydrophilic group, such as acrylic resin, polyester
resin, epoxy resin, alkyd resin, polybutadiene resin,
polyalkadiene resin, polyurethane resin, polyurea resin,
fluorine resin, silicone resin, amino resin, phenol resin,
vinyl resin, etc. of which are modified by introducing the
ionic or nonioni group (these binder is known in the field
of aqueous paint, aqueous ink and water-developable printing
plates); three dimensionally crosslinked resin particles
with an ionic group having a particle siæe of 0.01 to 5
micron, such as polymer particles prepared from aliphatic
diene monomers and acryl monomers; an organic solvent-
soluble polymer binder, such as rubber polymers (e.g.
polybutadiene, polyisoprene, styrene-isoprene~sty}ene
copolymer), acyl resin, polyester resin, epoxy resin, alkyd
resin, polyurethane resin, polyurea resin, fluorine resin,
silicone resin, amino resin, phenol resin, etc.; and the
like.
The radically polymerizable monomer (b) employed in

~C.~$~2
the present invention is not limited as long as a monomer
has an ethylenically unsaturated group, for example
(meth)acrylate, such as methyl (meth)acrylate, ethyl
(meth)acrylate, n-propyl (meth)acrylate, beta-hydroxyethyl
(meth)acrylate, beta-hydroxypropyl (meth)acrylate,
polyethyleneglycol mono(meth)acrylate, polypropyleneglycol
mono(meth)acrylate, polyethyleneglycol di(meth)acrylate,
polypropyleneglycol di(meth)acrylate,
methoxypolyethyleneglycol mono(meth)acrylate,
ethoxypolyethyleneglycol (meth)acrylate, glycerol
di(meth)acrylate, pentaerythritol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, tetramethylolmethane
tetra(meth)acrylate, ethyleneglycol diglycidyl ether
di(meth)acrylate, polyethyleneglycol diglycidyl ether
di(meth)acrylate, 1,4-butanediol di(meth)acrylate and 1,6-
hexanediol di(meth)acrylate; (meth)acrylamide, such as
~meth)acrylamide, N-methylol (meth)acrylamide, n-
butoxymethyl (meth)acrylamide, i-butoxymethyl
(meth)acrylamide, N-t-butyl (meth)acrylamide,
methylenebis((meth)acrylamide), ethylenebis
((meth)acrylamide) and propylenebis ((meth)acrylamide); and
the like.
The sensitizing dye (c) of the present invention is
not limited and can be anyone which is used in this field.
Typical examples of the dyes are xanthenes, such as rose
bengal, eosine, erythrosine B, Huoresein, rhodamine B and
the like; thiazines, such as methylene blue, thionine and

- 6 -
the like; chlorophills; quinones, such as Atromentine,
Muscarufine, EIelindon, Yellow CG, Helinedon Brown CM and CV,
alukanine, naphthazaline, alizarine and the like; indigos,
such as thioindigo; porphyrins, such as phthalocyanines;
ruthenium complexes, such as trisbipyrizine ruthenium
complex salts; and the like. Preferred are rose bengal,
eosine and methylene blue.
The photopolymerization initiator (d) of the
present invention is preferably required to be excited by a
light o~ a different wave length from a light which excites
the sensitizing dye. Examples of the initiators are benzoin
alkyl ether, such as benzoin methyl ether and benzain
isopropyl ether; benzophenones, such as benzophenone, o-
benzoyl benzoic methyl, N,N'-tetraethyl-4,4'-
diaminobenzophenone and Michler's ketone; acetophenones,such as 2,2-diethoxy acetophenone, 2,2-dimethoxy-2-phenyl
acetophenone, alpha-hydroxycyclohexyl phenyl ketone and 2-
hydroxy-2-methyl-1-phenyl-1-one; camphorquinone; a
combination of a bromide or amine compound with
ethylanthraquinone, 1,4'-diethylthioxanthone, benzyl, 1-
phenyl-1,2-propanedione, methylbenzoyl formate, 2,3-
butandiones and the like; a combination of a radical
generator (e.g. N-phenylglycines, diaryliodonium salts,
peroxides, peroxiesters, organic halides etc.) and a dye
(e.g. thioxanthene dye, cumarine dye, merocyanine dye,
thioxanthone dye, titanocene dye etc.); and the like. The
initiator (d) is selected such that the initiator is excited

3~
by a light having a different wave length ~rom a light which
excites the sensitizing dye. Typically, since the
sensitizing dye generally has a maximum absorption wave
length within the range of 400 to 800 nm, the initiator (d)
preferably has a maximum absorption wave length of 300 to
500 nm.
The photosensitive resin composition of the present
invention may further contain a solvent (e.g. water,
alcohols, etc.) and additives (e.g. a plasticizer, a
polymerization inhibitor, an anti-aging agent t etc.), if
necessary.
In the photosensitive resin composition of the
present invention, the dye (c) and initiator (d) are both
present in a catalystic amcunt in the composition.
Typically the dye (c) is present in an amount of 0.0001 to 5
parts by weight, preferably 0.0005 to 2 parts by weight,
more preferably 0.005 to l part by weight and the initiator
(d) is in an amount of 0.01 to lS parts by weight,
preferably 0.05 to lO parts by weight, more preferably 0.2
to 5 parts by weight, based on 100 parts by weight of the
total of the binder (a) and the monomer (b). If the dye (c)
is less than 0.0001 part by weight, the dissolved oxygen is
not effectively removed during the bump exposure and, if it
is more than 5 parts by weight, the dye absorbs the
irradiated light so as not to sufficiently remove the
dissolved oxygen and the resin composition also has dark
color. If the lnitiator is less than 0.01 part by weight,

`` - 8 2 ~ 2 ~
the curing i5 poor and, i~ it is more than 15 parts by
weight, the curing is proceeded around the surface and the
curing near the bottom is poor. A weight ratio of the
monomer (b) / the binder (a) is within the range of 0.1/99.1
to 1/99 to 99/1. If the monomer (b) is less thant the above
range, film-forming ability is poor and, if it is more than
the range, the toughness of the cured film is poor.
The resin composition may be prepared by mixing the
above mentioned components by a conventional method, such as
a kneader or if necessary with the solvent.
The photosensitive resin composition is generally
applied on a substrate to form a photosensitive resin
plate. Examples of the substrates are aluminum plate,
polyester sheet, copper plate, zinc plate, chromium plated
plate, glass plate, iron plate and the like. The
application can be conducted by coating or extruding. The
photosensitive resin layer preferably has a thickness of 0.1
to 10 mm. The resin plate may be covered with a film (e.g.
~icelon available from Nippon Synthetic Chemical Industry
Co., Ltd.) to prevent from oxygen invading into the resin
layer. When the resin composition of the present invention
is employed as W paint, it is applied by spray coating,
roll coating, dipping and the like after if necessary
diluting with a thinner. The film thickness of the W paint
preferably is within the range of 1 to 200 micron.
In the present invention, the resin plate is
preliminary exposed to a light to quench oxygen which is

-~ - 9
~3~2~
dissolved in the resin layer. The light for the preliminary
exposure has a wave length range which only excites the
sensitizing dye (c) and which does not excites the
photopolymerization initiator (d). In the relation between
the qensti2ing dye ~c) and the intiator (d), if the maximum
light absorption wave length of lhe dye (c) is
expressed ~max(c) and that of the intiator (d) is
expressed ~max(d) ~ it is preferred that ~max(c) is within
the range of 450 to 800 nm and ~lax(d) is within -the range
of 300 to 400 nm. The difference of them satisfies the
following formula.
¦~max(c) ~ max(d)¦ > 100 nm
If the above formula is satisfied, the preliminary (bump)
and main exposures are conducted most effectively Most
preferred is a combination of rose bengal, eocine Y,
methylene blue as the dye (c) and benzoine e-thers as the
initiator (d). The exposure is conducted over all surface
of the resin plate. The exposing time is not limited but
generally 10 seconds to 120 minutes. The light source
includes an incandescent lamp, a fluorescent lamp, a
chemical lamp, an intermediate or high pressure mercury
lamp, a halide lamp and the like. If the light source
produces a light which excites the initiator, such wave
length light should be cut off by a conventional filter.
After the preliminary exposure (bump), the main
exposure is conducted through a negative by a conventional
method. The light for the main exposure is not so limited,

10 --
~3~
because any light can be used as long as it includes a wave
length range which excites the initiator (d). The light
sources are three type;
I. a light source which only exites the initiator.
II. a light source which exites not only the initiator
but also the sinsitizing dye.
III. a co~bination of a light which exites the initiator
and a light which exites the sensitizing dye.
The type II and III is preferred because of an inhibiting
function of dissolving oxygen into the resin layer during
the main exposure. In case of a three dimensional imaging
system using a laser light, although it takes a long time
for a main exposure, the light source of type III
effectively inhibits it during the main exposure. Examples
of the lights are ultraviolet beams. The exposing time is
not limited but typically 3 seconds to 30 minutes.
After the main exposure, the resin plate is
developed to produce printing images. The development can
be carried out by a conventional method with a solvent (e.g.
water or alkaline water; alcohols; halogenated hydrocarbons,
such as trichloroethane and tetrachloroethane; aromatic
hydrocarbons, such as toluene and xylene) or using physical
means (e.g. brushing).
The oxygen quenching mechanism of the present
invention is not understood, but is believed as follow. The
preliminary exposure excites the sensitizing dye (c) and the
excited energy is transferred onto the oxygen dissolved in

h~ 3
the resin layer. The excited oxygen is addition-reacted
with the double bonds in the monomer (b), so that the oxygen
which prevents polymerization reaction is quenched in the
monomer. Accordingly, in the main exposure, polymerization
reactions are smoothly proceeded and can avoid ununiformity
of polymerization, especially in the thickness direction.
Isolated dots are faithfully produced without side etching
and the etching depth of white portions and dot portions is
deep.
The photocurable resin composition of the present
invention can quench the dissolvecl oxygen before main curing
and polymerization reactions in the main exposure are
ideally proceeded and therefore can be widely applicable to
photoresists for electronic elements, three dimensional
imaging system, adhesives including dental fields and
coatings. Especially in flexographic printing, since the
inhibition of polymerization does not occur, an exposing
time at the main exposure can reduce to obtain thinner
images than negative images and avoid dot gain.
EXAMPLES
The present invention is illustrated by the
following Examples which, however, are not construed as
limiting the present invention to their details.
Examples 1 to 3 and Comparative ~xamples 1 to 4
A sensitizing dye listed in ~able 1 and 40 parts by
weight of a partially saponified polyvinyl acetate (a
polymerization degree of 500 and a saponification degree of

~ - 12 -
~3~,2~
80 mol %) were mixed in 60 parts by weight of water to form
a solution. To the solution, 15 parts by weight of glycerol
monomethacrylate, 15 parts by weight of glycerol
dimethacrylate, 1.2 parts by weight of 2,2-dimethoxy-2-
phenylacetophenone and 0.08 parts by weight of 2,6-di-t-
butyl-4-methylphenol were mixed to obtain a uniform
photosensitive resin composition.
The resulting composition was poured on an iron
plate havinq an anti-halation layer and heat-dried in a dark
place for one day to obtain a resin plate having a resin
layer of 1.0 mm. On the resin layer, a polyvinyl alcohol
film (~icelon available from Nippon Synthetic Chemical
Industry Co., Ltd.) having 16 micrometer was laminated. The
resin plate was ~ubjected to a preliminary exposu~e at
irradiation conditions as shown in Table 1 with a light
source through a filter as shown in Table 1. Then, a
negative film was closely contact under vacuum and then
main-exposed to a light as shown in Table 1 to cure. If the
same light source was employed in Table 1, a filter was
employed in the preliminary exposure and then was taken
off. Thereafter, the negative film was removed and
developed by spraying water of 40 C at a water pressure of
4 Kg/cm2 for 2 minutes, and then dried at 90 C for 10
minutes in a drying apparatus.
Measurements were made on diameters of minumal
isolated dots of the reproduced images, side-etched or not,
a depth of hole having 3.5 mm diameter and a depth of 65
.,

1 3 ~ b~
line 90 g~ reverse hol~ dot~ portions. The re~ult~ are ~hown
in Table 1.

- 14 ~ 3 ~ ~
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. ~. n n rr o o o o c~ O c~ , ~ u) rr
o n ro 3 c n 3 V ~n o O V
o ~t ~ o. o ~ _3 ~7 ~ 3 r~ ~ o ~: `C
o ~S ~ O ~ . O n o n cL o
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- 15 ~ 3~
1 A dye having ~max 558 nm
2 A dye having ~max 518 nm
3 A filter cutting off less than 450 nm available
from Kimoto Co., Ltd.
4 35 mm diameter
reverse
Example 4
A photosensitive resin composition was prepared by
mixing 66.5 parts by weight of three-dimensionally
crosslinked polymer particles (80 mol % of butadiene, 6.5
mol ~ of methacrylic acid, 1 mol ~ of divinylbenzene and
12.5 mol % of methyl methacrylate and having a particle size
of 0.06 micron), 8 parts by weight of N,N-
dimethylaminepropyl methacrylamide, 6 parts by weight of
phenoxyethoxy ethanol, 12 parts by weight of lauryl
methacrylate, 5 parts by weight of trimethylolpropane
triacrylate, 2 parts by weight of 2,2-dimethoxy-2-phenyl
acetophenone, 0.5 parts by weight of 2,6-di-t-butyl-4-
methylphenol and 0.0075 parts by weight of Rose Bengal at 60
~ C, using a double roll and a kneader. The resin
composition was extruded onto an iron plate to obtain a
photosensitive resin plate having about 0.4 mm resin layer.
On the resin layer, a matte f.inish, which was
prepared by mixing 15 g of hydroxycellulose and 95 g of
distilled water and then disperse therein 4 g of silica
having an average particle size of 15 micrometer, was coated
to form a matte coat of 3 mlcrometer, and then dried at 70

C for 2 minutes.
The resulting resin plate was preliminary exposed,
or bumped with the light though the filter and exposing
conditions as shown in Table 2. After remove the filter if
used, a negative film was closely contacted with the resin
layer and main-exposed to light to cure. The negative film
was removed and developed with water at 40 C for 2 minutes,
uslng ~ brus~ elutlsn ~v~lop0r ~nd pos~-cu~d ln a drying
room at llO C for 2 minutes under a 2 KW high pressure
mercury lamp. The resulting imaged plate was subjected to
an evaluation of images and the results are shown in Table
2.
Example 5
A resin plate was prepared as generally described
in Example 4, with the exception that a copolymer was
prepared from 79 mol ~ of butadiene, 6.7 mol ~ of
methacrylic acid, 1.3 mol % of ethyleneglycol dimethacrylate
and 13 mol % of methyl methacrylate was employed. The same
evaluation was made and the results are shown in Table 2.
Comparative Example 5
The same procedure and evaluation of Example 5 were
repeated except that Rose Bengal was not employed and the
results are shown in Table 2.
Comparative Example 6
The same procedure and evaluation of Example 4 were
repeated except that Rose Bengal was not employed and the
results are shown in Table 2.

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~: ~
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1:: U~
JJ D
o u~ ,~ E c~ E ,
~o . ~
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.,~~.,1 ~ 0~ 0 ~ _ O O
X
D Eo 5
E~ ~~ ~1~ o Ll E E E E ~ c~
Eà ~ O ,~ E ~ O ~D o
.,~ o~~ h U
~ ~JU~ U O ~ ~ o~
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-- 8~ --

- 19 - 2~3~2
Example 6
A photosensitivfe resin composition was prepared by
dissolving 0.05 mol of 2-ethylanthraquinone; 0.05 mol of
carbon tetrabromide, 0.25 mol of N-methyldiethanolamine and
0.5 g of rose bengal in a mixture of 500 g of an oligomer
(available from Shin Nakamura Chemical Industry K.K. as NK
Ester BPE-1300).
Three gram of the resin composition was charged in
an aluminum cylindrical can having a depth of 7 mm and a
diameter of 55 mm and exposed (bumped) to an yellow lamp for
15 minutes at a distance of 5 cm. While the bump continued,
it was irradiated by a 15 mV He-Cd laser available from
Omunichrome Company at a scanning mode of 15 mm/sec to
obtain a cured article.